Characterization of NiTi Shape Memory Alloy Sintered at Different Temperatures in Reducing Environment

2020 ◽  
Vol 1010 ◽  
pp. 632-637
Author(s):  
Hafizah Hanim Mohd Zaki ◽  
Nur Azemuzahir Mohd Sobri ◽  
Jamaluddin Abdullah ◽  
Norshahida Sariffudin ◽  
Farah Diana Mohd Daud
Keyword(s):  
Solid State ◽  
Shape Memory ◽  
Phase Formation ◽  
Single Phase ◽  
Reducing Agent ◽  
Niti Shape Memory Alloy ◽  
Transformation Behavior ◽  
Formidable Challenge ◽  
Different Temperatures ◽  
Reducing Environment

NiTi has received significant interest as medical implant materials due to its shape memory effect behavior apart from its good biocompatibility and mechanical properties. The formidable challenge of obtaining single phase NiTi from elemental powders via solid state is due to oxidation problem of elemental powders and the oxygen atoms dissolve in NiTi matrix as interstitial impurities forming stable oxygen-rich TiNiOx. This may deterioriate the shape memory behavior of NiTi. This research investigates the use of MgH2 in combination with CaH2 as in-situ reducing agent to eliminate oxidation of the specimen during sintering both at lower and higher sintering temperatures. Here, the effect of sintering temperature on phase formation and transformation behavior of NiTi in reducing environment was studied. The phase formation was characterized by using x-ray diffraction (XRD) where the morphology and elemental analysis were characterized by using the scanning electron microscope (SEM) equipped with EDS. The martensitic transformation behavior was analyzed using differential scanning calorimeter (DSC). The use of MgH2 and CaH2 as reducing agent has a significant influence on the phase formation of NiTi synthesized via solid state especially at 930 °C, where almost single phase NiTi was formed with good transformation behavior. This reducing agent creates a conducive environment for the production of single phase NiTi.

Preparation of Ultra–Fine La3NbO7 Powder by Solid State Reaction

2012 ◽  
Vol 512-515 ◽  
pp. 158-161 ◽  
Author(s):  
Ling Dai ◽  
Qiang Xu ◽  
Shi Zhen Zhu ◽  
Ling Liu
Keyword(s):  
Solid State ◽  
Solid State Reaction ◽  
Single Phase ◽  
Thermal Barrier ◽  
X Ray Diffraction ◽  
X Ray ◽  
Granular Particle ◽  
Fine Particle Size ◽  
Ultra Fine Particle ◽  
Different Temperatures

As a new candidate material for the ceramic layer in thermal barrier coatings (TBCs) system, La3NbO7 was synthesized with La2O3 powder and Nb2O5 powder by solid state reaction. The stating powders with a mole ratio of La to Nb of 3:1 were mixed and then the mixture was calcined under the different temperatures(800°C, 1000°C, 1200°C) and dwell times(2h, 6h, 10h). The phase structure of the powder was observed by X–ray diffraction(XRD), and the microstructure of the sample was observed by scanning electron microscope(SEM). The effect of calcination temperature and dwell Time on the phase formation were examined. The results indicate that the La3NbO7 powder with single phase can be synthesized successfully at 1200°C for 10h in air, and the La3NbOsub>7 powders synthesized have an ultra-fine particle size of 0.5˜1µm with a granular particle shape. With the temperature increasing, LaNbO4/sub> was synthesized firstly and then La3NbO7 was synthesized with a mole ratio of La2O3 to LaNbO4 of 1:1.

Study on the Phase Formation of Corundum-Type Mg4Nb2O9 Powders by the Solid-State Process

2012 ◽  
Vol 499 ◽  
pp. 174-177
Author(s):  
Yi Shan Jiang ◽  
Ying Zi Wang ◽  
Ya Ming Chen ◽  
Yun Long Yue ◽  
Hai Tao Wu
Keyword(s):  
Phase Composition ◽  
Solid State ◽  
Phase Formation ◽  
Single Phase ◽  
Magnesium Niobate ◽  
Calcination Temperatures ◽  
Air Atmosphere ◽  
State Process

The corundum-type magnesium niobate, Mg4Nb2O9, powders were synthesized by the conventional solid-state process. The mixtures of MgO and Nb2O5were calcined in the temperature ranging from 500°C to 1200°C for crystallization in air atmosphere. The formation of the Mg4Nb2O9phase was investigated as a function of calcination temperatures by DTA and XRD. The morphology and phase composition were determined via a combination of SEM and EDX techniques. The results showed that the single-phase Mg4Nb2O9could be obtained at 1050°C for 2h with the size of less than 5μm.

NiTi Shape Memory Alloy Wire’s Constitutive Describe at Different Temperatures

2017 ◽  
Vol 729 ◽  
pp. 13-17
Author(s):  
Guang Yong Yang ◽  
Yang Zhong ◽  
Zhi Fei Qiu ◽  
Jun Wang ◽  
Wei Na Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Niti Shape Memory Alloy ◽  
Thermal And Mechanical Properties ◽  
Restoring Force ◽  
Intelligent Material ◽  
Different Temperatures ◽  
Relationship Of ◽  
The Relationship

NiTi shape memory alloy is an intelligent drive and awareness materials which develop very rapidly and is used in many fields in recent years, whose mechanical properties are not only related to chemical composition, but also closely related to the temperature. This article aims to study the NiTi shape memory alloy wire’s constitutive behavior coupled thermal and mechanical properties at different temperatures. By analyzing the results, the relationship of NiTi shape memory alloy between deformation and the restoring force at elevated temperature is obtained, thus providing a basis for the engineering design and simulation process of NiTi intelligent material.

Thermoelectric properties of bulk MoSi2 synthesized by solid state microwave heating

2016 ◽  
Vol 30 (19) ◽  
pp. 1650234 ◽  
Author(s):  
Yu Lan ◽  
Mianyu Xie ◽  
Ting Ouyang ◽  
Song Yue
Keyword(s):  
Solid State ◽  
Microwave Heating ◽  
Single Phase ◽  
Sintering Temperature ◽  
Seebeck Coefficients ◽  
Long Duration ◽  
Powder Factor ◽  
High Efficient ◽  
Different Temperatures ◽  
Precursor Powders

In this research, single phase [Formula: see text]-MoSi2 was prepared by solid state hybrid microwave heating within 90 min at relatively low temperature 1273 K. Such precursor powders were then ball milled and sintered by microwave heating at different temperatures. The thermoelectric (TE) properties of MoSi2 bulks were investigated in the temperature range of 300–673 K. When the sintering temperature increases from 973 K to 1273 K, the electrical resistivity decreases significantly and the Seebeck coefficients increase obviously, leading to the maximum TE powder factor of [Formula: see text] at 673 K. These results demonstrate the feasibility of high efficient and economical synthesis of MoSi2 by microwave heating technique, with the final products having comparable TE performance in comparison to those from typical methods with long duration and energy-extensive consumption.

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